The role of the PZP domain of AF10 in acute leukemia driven by AF10 translocations

Abstract

Chromosomal translocations of the AF10 (or MLLT10) gene are frequently found in acute leukemias. Here, we show that the PZP domain of AF10 (AF10PZP), which is consistently impaired or deleted in leukemogenic AF10 translocations, plays a critical role in blocking malignant transformation. Incorporation of functional AF10PZP into the leukemogenic CALM-AF10 fusion prevents the transforming activity of the fusion in bone marrow-derived hematopoietic stem and progenitor cells in vitro and in vivo and abrogates CALM-AF10-mediated leukemogenesis in vivo. Crystallographic, biochemical and mutagenesis studies reveal that AF10PZP binds to the nucleosome core particle through multivalent contacts with the histone H3 tail and DNA and associates with chromatin in cells, colocalizing with active methylation marks and discriminating against the repressive H3K27me3 mark. AF10PZP promotes nuclear localization of CALM-AF10 and is required for association with chromatin. Our data indicate that the disruption of AF10PZP function in the CALM-AF10 fusion directly leads to transformation, whereas the inclusion of AF10PZP downregulates Hoxa genes and reverses cellular transformation. Our findings highlight the molecular mechanism by which AF10 targets chromatin and suggest a model for the AF10PZP-dependent CALM-AF10-mediated leukemogenesis.

Acute Undifferentiated Leukemia With a Balanced t(5;10)(q35;p12) Resulting in Fusion ofHNRNPH1WithMLLT10

“…LAP was shown to mediate protein-protein interactions and homo-oligomerization of recombinant MLLT10 in vitro (40). Recently, disruption of LAP in MLLT10 fusion proteins was found to lead to malignant transformation (41). Towards its C-terminal end (amino acids 731-794 in NP_004632.1), the MLLT10 protein has a coiled-coil domain which contains a conserved octapeptide (EQLLERQW) motif separated by a short non-conserved sequence from a leucine zipper domain (42).…”

Atypical histone targets of PHD fingers

“…Two PHD fingers linked by a single zinc finger form an integrated module, the PZP domain (PHD-Zn-knuckle-PHD). Structural studies of PZPs from BRPF1, AF10, and PHF14 reveal a very similar saddle-like globular fold of this domain, which is stabilized by five zinc-binding clusters ( 49 , 50 , 51 , 52 , 53 ), and all PZPs have been shown to bind to unmodified histone H3 tail, but not identically. While the first PHD finger (PHD1) of PZP from BRPF1, AF10, and PHF14 interacts with the N-terminal region of H3 (residues A1-T6) in a manner similar to a typical PHD finger, PZPs of AF10 and PHF14 also recognize the middle region of histone H3 tail (residues L20-S28) ( Fig.…”

“…In-depth biochemical and in vivo analyses of PZPs underscore the significance of the interactions of this domain for proper functions of the PZP-containing proteins, including BRPF1/2/3, AF10/AF17, JADE1/2/3, and PHF14. AF10/A17 is a cofactor of the H3K79 methyltransferase DOT1L, and binding of AF10/AF17 PZP to H3 is required for H3K79 dimethylation and spreading of the H3K79me2 mark ( 49 , 52 ). It has been shown that PZP of AF10 engages the nucleosome through multivalent interactions with the entire H3 tail as well as DNA and that incorporation of functional PZP in leukemogenic CALM-AF10 fusions blocks the transforming activity in vitro and in vivo and abolishes CALM-AF10–driven leukemogenesis in vivo ( 52 ).…”

“…AF10/A17 is a cofactor of the H3K79 methyltransferase DOT1L, and binding of AF10/AF17 PZP to H3 is required for H3K79 dimethylation and spreading of the H3K79me2 mark ( 49 , 52 ). It has been shown that PZP of AF10 engages the nucleosome through multivalent interactions with the entire H3 tail as well as DNA and that incorporation of functional PZP in leukemogenic CALM-AF10 fusions blocks the transforming activity in vitro and in vivo and abolishes CALM-AF10–driven leukemogenesis in vivo ( 52 ). Functional PZP of BRPF1 is necessary for the recruitment of the acetyltransferase MOZ/MORF complexes to chromatin and enzymatic functions of these complexes ( 50 , 54 ).…”

CXCR4 Mediates Enhanced Cell Migration in CALM-AF10 Leukemia

“…The PHD1-zinc-knuckle-PHD2 (PZP) domain of AF10 is consistently interrupted in CALM-AF10 translocations. It has been recently identified that the disruption of the PZP domain of AF10 disrupts the normal localization of DOT1L across the genome, allowing DOT1L to be tethered to the HOXA locus by CALM-AF10 (28). CALM-AF10 leukemias typically show a poor response to therapy, have an increased propensity to relapse and have a worse overall prognosis.…”